The basic purpose is to identify the importance of genetic factors in the etiology and pathogenesis of various forms of experimental hypertension. Since different mechanisms are involved in the various available forms, presumably they will differ in the degree to which genetic factors are important. Of necessity, such a study also involves obtaining further information on other factors which influence the development and course of each of the types of hypertension being examined, since only by understanding the nature of the disease processes can one determine how the alterations due to genetic constitution might be brought about. Therefore it is proposed to study various strains of rats, various genetic crosses between strains, and determine how, and hopefully why, they differ in their susceptibility and response to influences tht cause hypertension. Bibliographic references: Hall, C.E., Ayachi, S., Eversole, W.J. and Hall, O. Evaluation of adrenal-regeneration hypertension in blinded rats. Endocrinology 96: 519-522, 1975; Hall, C.E., Ayachi, S. and Hall, O. Hypertension in consequence of injury to the adrenal gland. Research on Steroids 6: 179-193, 1975.